1. Field of the Invention
The present invention relates to a thermal connector for a printed circuit card equipped with electronic components dissipating heat, the connector being intended more particularly for electronic cabinets with a high density of cards.
2. Description of the Prior Art
The problem of thermal connection appears in particular in electrical apparatus or equipment having a large number of cards equipped with electronic components, because some of these components dissipate a large amount of heat which should be evacuated under the best possible conditions in order to keep the components under acceptable working conditions. It is known, for example, that integrated circuits contain more and more functions and elements integrated on the semiconductor chip and that the amount of heat dissipated increases correlatively. In order not to damage the circuits or reduce their lifetime, their working junction temperature should not exceed about 125.degree. C., and hence it is desirable to evacuate the heat dissipated by these circuits as fast as possible.
To do this, it is common practice to use printed circuit cards equipped with a heat-conducting substrate. Such cards are described, for example, in French patent application No. 82 05253 published under U.S. Pat. No. 2,524,250. These cards are generally mounted in connectors linking the heat-conducting substrate of the card with the cold wall or walls of the electronic equipment to be cooled. The cold walls then carry the heat units toward the heat sink of the system. In the case of the thermal connectors described above, the heat conduction chain contains the following links:
the coupling resistance of the housing on the card, PA1 the transverse conduction resistance of the card, PA1 the longitudinal conduction resistance of the heat-conducting substrate of the card which is higher in proportion to the dimension of the card, PA1 the coupling resistance of the lateral edges of the heat-conducting substrate on the cold walls of the equipment, and PA1 the conduction resistance of the frame of the equipment between the cold walls and the heat sink. PA1 the coupling resistance of the components on the conductive substrate, PA1 the transverse conduction resistance of the substrate of the card, PA1 the longitudinal conduction resistance of the heat-conducting substrate, and PA1 the coupling resistance of the lateral edges of the heat-conducting substrate directly on the heat sink.
This chain of heat conduction is relatively long. Thus, in order that, in particular, the last link will not alter too extensively the evacuation of the heat dissipated by the system, the dimensions of the equipment receiving this type of connector should be limited to a few dozen centimeters and the electronics should be concentrated in a limited volume. These constraints are therefore incompatible with the volume of the electronic cabinets such as, for example, the bays of telecommunication equipment or even the new generations of large satellites for which the electronic parts situated at the center are too far from the cold outside walls that radiate the heat into space.
It would be desirable to remedy these drawbacks by providing a thermal connector having a very short chain of heat conduction in which the links constituted by the cold wall and its connection to the heat sink are eliminated.